In the past year we have demonstrated that a fragment of the large plasmid required for Crown gall tumor induction by Agrobacterium tumefaciens is stably incorporated into the plant tumor. The experiments we shall conduct during the coming year relate to this observation. We will determine if all tumors contain this same fragment independent of the strain of Agrobacterium which induces the tumor or the plan in which it is induced. Secondly, we shall determine if the bacterial DNA is integrated into the plant genome or whether it replicates as a self perpetuating unit in the cytoplasm of the plant cell. Thirdly, we shall determine whether the phenotypic reversion of the tumor cell to a normal cell is accompanied by the loss of the plasmid fragment. Our data thus far have shown an analogy between plant tumors and certain animal tumors. The studies which we hope to accomplish in this coming year should give a strong indication of how far this analogy extends. BIBLIOGRAPHIC REFERENCES: Merlo, D.J., and E.W. Nester. Plasmids in Avirulent Strains of Agrobacterium. J. Bact. 129:76-80 (1977). Montoya, A.L., Chilton, M.-D., Gordon, M.P., Sciaky, D., and E.W. Nester. Octopine and Nopaline Metabolism in Agrobacterium tumefaciens and Crown Gall Tumor Cells: Role of Plasmid Genes. J. Bact. 129:101-107 (1977).